The present invention relates to automotive vehicles, and in particular to an apparatus and method for controlling throttle position.
Throttle control is important in maintaining fuel efficiency and preventing speed drop when engine loads are applied during idling. Throttle position is typically maintained through the use of a control device. This control device receives position feedback from a throttle position sensor, analyzes the feedback, and manipulates the throttle actuator. An important aspect of such a control device is its ability to establish an operating position and repeatedly maintain that position without excessive variation.
Prior devices have used discretized feedback to maintain this repeatability and control. The feedback signal is implemented as an analog feedback voltage. The feedback voltage enters an analog-to-digital (AtoD) converter. The AtoD converter then converts the analog signal into a plurality of discrete levels dependent on its input voltage. The range of voltage between zero and the reference voltage is partitioned into the total number of levels, typically 2(No. of bits). Therefore, to a controller, the digital output from an analog input at the top of a voltage interval is the same as the digital output from an analog input at the bottom of a voltage interval. As a result, single digital level corresponds to a range of analog voltages, and thus, a range of actual positions.
Typical throttle position feedback control systems assign a desired set point to a discretized level. The set point is the desired operating position of the throttle. Within the control system, the discretized feedback level is compared with the set point level. If the feedback level is different than the set point level, the control device recognizes the variance and corrects the throttle position. If the feedback level is the same as the set point level, the control device does not recognize any error or variance and does not issue any correction. This allows the feedback voltage to drift within the set level without any sensed error, which allows the throttle position in turn to drift within the interval without any correction. The drifting creates a lack of repeatability and fine motion control. Fine motion control is the ability to obtain positions within a minute range after a general range has been achieved. By way of example, if the command positions is 2 and the descretization level is xe2x85x9, then the actual position may be any throttle position between 1 {fraction (15/16)} and 2 {fraction (1/16)}. This lack of repeatability and fine motion control creates problems in electronic throttle systems during idling. Because the throttle position in current devices is allowed to drift within the voltage interval engine idle speed control is degraded.
Furthermore, current control systems typically experience hysteresis in the feedback control sensor. Hysteresis is a property of a sensor which makes sensor output dependent on movement direction. Therefore, in a sensor experiencing hysteresis, the sensed motion lags the actual motion. The hysteresis causes inaccuracy and variability because throttle position error depends on the direction of travel. A new control system is therefore needed to improve repeatability and eliminate feedback sensor hysteresis.
An embodiment of the invention includes at least one sensor for detecting throttle position and translating said throttle position into an analog signal. The signal is then sent to an AtoD converter which converts the analog signal into multiple discrete feedback levels. A controller determines a desired throttle position and establishes the desired throttle position between two discrete feedback levels. The controller then compares the discrete feedback level with the desired throttle position and determines a correction effort based on the comparison. An adjusting means receives the correction effort and adjusts the throttle position in accordance with the correction effort.
In another aspect of the invention, an embodiment of a method of controlling throttle position is provided. The method includes the steps of detecting a throttle position and translating the throttle position into a feedback voltage. The method then encodes the feedback voltage from the throttle into a plurality of discrete feedback levels. A desired throttle position is established, and the desired throttle position between two of said discrete feedback levels is located. These feedback levels are compared to the desired throttle position set point, and the throttle position is adjusted based on the comparison.
A third embodiment includes one or more sensors for detecting at least one valve position and translating the position into an analog signal. These signals are fed into at least one AtoD converter. The AtoD converter transforms the analog signal into a plurality of feedback levels. A controller then determines a desired valve position. The controller places the desired valve position between two discrete feedback levels and compares the discrete feedback level with the desired valve position. The controller determines a corrective effort based on the comparison. The controller sends the corrective effort to an adjusting means, which adjusts the valve position in accordance with the correction effort.
In another aspect of the invention, an embodiment of a method of controlling valve position is provided. The method includes the steps of determining valve position and translating the valve into at least one feedback voltage. These voltages are encoded into a plurality of discrete levels. A desired valve position is established. The method then locates the desired valve position between two of the discrete feedback levels. The desired valve position is compared with the feedback levels and the valve position is adjusted based on the comparison.
Other systems, methods, features, and advantages of the invention will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, within the scope of the invention, and protected by the accompanying claims.